Molecular biological study of MDV is proposed for the understanding of the mechanism of tumor induction by MDV in chickens. MDV and herpes virus of turkey (HVT) DNA will be cleaved with restriction enzymes and the physical maps will be constructed. The minor homology selected in DNA of HVT and MDV will be further studied in detail in regard to size, location, degree of homology and transcription of these homologous sequences. The state of virus genome and virus genome transcription will be studied in JMV transplantable tumors, in comparison to the tumors induced by MDV infection. After the physical mapping will be completed, the transcriptional map will be constructed for virus genome expression in tumors, and established transformed cell lines. To assist all the proposed studies, virus DNA fragments will be cloned by pBR 322 plasmid and by Lambda WES system and Charon phage 3, 4, 16, and 21.